An automobile seat belt device has a structure such that a webbing withdrawn from a retractor and hung through an anchor member can restrain an occupant. As the anchor member, a member referred to as a shoulder anchor, through anchor, through ring, or the like, which is fixed to a B pillar or the like, is used in many cases.
PTL 1 describes that a small roller is provided on an anchor member in order to facilitate withdrawal and retraction of the webbing. However, an adequate effect is not necessarily obtained.
Furthermore, it has been a conventional practice to improve webbing withdrawing and retracting performance by reducing friction between a webbing and an anchor member. As the treatment agent therefor, there have been proposed a coating treatment agent containing a blocked urethane prepolymer compound (PTL 2), a polyether-polyester compound-based treatment agent (for example, PTL 3), a treatment agent containing as a major component a composition including a branched alcohol ester of a higher fatty acid and a nonionic surfactant (PTL 4), and the like.